array_push(), array_unshift() adds variables by value (variables are dereferenced)
array_push(), array_unshift() adds variables by value (variables are dereferenced)

fixes https://github.com/peachpiecompiler/peachpie/issues/600
updates https://github.com/peachpiecompiler/peachpie/issues/573#issuecomment-571592714

iolevel/peachpie-concept,iolevel/peachpie,iolevel/peachpie-concept,iolevel/peachpie,iolevel/peachpie-concept,peachpiecompiler/peachpie,peachpiecompiler/peachpie,peachpiecompiler/peachpie,iolevel/peachpie